Laminated glass is less likely to scatter even when shattered by external impact and can be safely used. Due to this advantage, laminated glass has been widely used, for example, in front, side, and rear windshields of vehicles including automobiles and windowpanes of aircraft, buildings, or the like. A known example of laminated glass is a type of laminated glass including at least a pair of glass plates integrated through, for example, an interlayer film for a laminated glass which contains a liquid plasticizer and a polyvinyl acetal resin.
Recently, the performance required of glass has been increasingly diversified. From the aspects of the design, privacy protection, and light shielding effect, a glass with a gradation pattern in which the color is smoothly changed from dark to light has been desired.
For example, in the case where the glass with a gradation pattern is used as a building window glass, the window can have an excellent design and can become opaque at a desired part to provide privacy protection. For another example, in the case where the glass with a gradation pattern is used as an automobile roof glass, the automobile roof can have an excellent design and can block light from the outside to control the light in the automobile.
As such a glass with a gradation pattern, Patent Literature 1 discloses an interlayer film for a laminated glass including a dark color section, a gradation section, and a transparent section, in which these sections are situated along side each other in the stated order in the direction orthogonal to the thickness direction.
However, for achieving highly excellent design, privacy protection, and light shielding effect, a single gradation pattern is not enough and the gradation pattern is desired to be changed with the situation. Moreover, according to the situation, the gradation pattern is desired to be turned off to set the glass in a transparent state. In any conventional glass with a gradation pattern, however, it has been difficult to change the gradation pattern at will or switch the display state to a transparent state.